Chair

ABSTRACT

A chair includes a seat, a backrest and a back frame having a rigid structure and arranged behind the backrest with an interval in between. The backrest is attached to the back frame by a first support device arranged at a height position close to an upper end of the backrest and by a second support device arranged at a position lower than the first support device and higher than a seat surface. The first support device is attached to a part close to a right-left middle part of the upper end part in the backrest. The second support device is attached to a left end part and a right end part of the backrest.

TECHNICAL FIELD

The present invention relates to a chair and, in particular, treats anoffice-use chair as a preferred object.

BACKGROUND ART

The first factor to be owned by a chair is comfort to a user. Inparticular, in a chair used in an office, a person continues sittingdown for a long time and hence comfort is an important factor. There aresome factors damaging comfort. Typically, such factors include a feelingof oppression caused by a situation that the portion hitting the body ishard and a feeling of tightness that the body cannot easily be moved.Thus, countermeasures are taken in order to reduce the feeling ofoppression and the feeling of tightness.

The problem of the feeling of oppression is handled such that a cushionis arranged in the seat or the backrest, the seat or the backrest isconstructed from a mesh, or the like. Adoption of a deformable structurein the seat plate or the backrest plate is also effective in improvingsoftness.

On the other hand, in order that the feeling of tightness may beprevented or reduced, it is sufficient that the movement of the body ina state of sitting down is permitted. Imparting a rocking function tothe chair is effective means for alleviating the feeling of tightness.Nevertheless, a simple rocking function alone has merely a limitedeffect in improving comfort. This is because a person takes variousattitudes in a state of sitting down and hence the simple rockingfunction cannot follow the changes in the attitude of the person.

For example, it is usual that a seat occupant twists the body so as toturn aside. Nevertheless, in a case that the backrest has a rigidstructure, when the person twists the body, the contact area with thebackrest decreases so that the user receives a feeling of oppression andhence comfort is degraded.

Thus, designs have been performed for improving the follow-up propertyof the backrest for the movement of the body. As examples of these, as astructure that the backrest can be deformed by the body pressure of aseat occupant, Documents 1 to 4 describes a configuration that abackrest is supported by the back frame at three positions consisting oftwo right and left positions in the upper end part and of the right-leftmiddle part of the lower end part.

In a case that the backrest is freely deformed by the body pressure ofthe seat occupant, the stability of the body is degraded and hencecomfort is degraded on the contrary. That is, the backrest is requiredto have a function of firmly supporting the body. In particular, in acase that a person sits on the chair and performs various kinds of deskwork, when the person slouches, the internal organs are pressed andhence an intense stress acts on the body. Thus, a high necessity isconcluded that even in a non-rocking state, the body (especially, thelumbar) of the person is supported and held in a state that the back isstraightened.

When the individual publicly known documents are viewed from theperspective of such a function of stably supporting the body, thebackrest of the individual publicly known documents is supported atthree positions consisting of two right and left positions at the upperend and of the right-left middle part of the lower end part. Thus, it isconcluded that excessive deformation is avoided. Nevertheless, since thelower part of the backrest is easily deformed, a high function of firmlysupporting the body in a non-rocking state and holding a state that theback is straightened is not expected. That is, in the individualpublicly known documents, there is the possibility of an insufficientfunction of stably supporting the body in a non-rocking state.

Further, as a use mode of a chair, it is usual that in a rocking state,the body is twisted right or left or, alternatively, the shoulder isdeviated right or left. In this case, the load is concentrated on theleft side or the right side of the upper part of the backrest.Nevertheless, in the individual publicly known documents, the upper partof the backrest cannot easily be deformed. Thus, a high follow-upproperty for the attitude change of the body is not expected and hence,also in this perspective, there is room for improvement of comfort.

Further, in many cases, the backrest of a chair is provided with a backplate fabricated from resin. Then, as means for alleviating the feelingof oppression and improving the cushioning property and the fitproperty, a configuration is employed that the back plate has a flexiblestructure. For example, in Document 5, the applicant of the presentapplication has disclosed that a large number of elongated grooveshorizontally elongated in the right and left directions are provided inthe back plate so that the body support part is constructed from themulti-stage band plate group. In this Document 5, in each band plate, inorder that deformation may easily occur, a thin trimming groove isprovided in the right and left end parts.

On the other hand, Document 6 discloses a back plate having aconfiguration similar to a honeycomb structure. Further, Document 7discloses a backrest in which cross-shaped holes andstraight-line-shaped holes are arranged regularly so that a structuresimilar to a mesh is formed.

In Documents 6 and 7, the body support part of the backrest is formed ina mesh structure. Then, a group of thin lines constituting the bodysupport part are individually bent and hence the thin lines are allowedto perform extensional deformation in accordance with the body pressure.Thus, the entire body support part can be deformed such as to becomeconcave rearward.

Here, the function of supporting the body achieved by the backrest isconsidered below. A high flexibility alone is not sufficient and thefunction of stably supporting the body is also important. For example,when there is a tendency that the body shakes in a rocking state, insome cases, comfort is degraded on the contrary.

Further, in a case that the seat occupant performs desk work like PCoperation in a non-rocking state, when the lumbar is firmly supported,an appropriate attitude in which the back is straightened is maintainedand hence this situation is preferable. In contrast, when theflexibility of the backrest is excessively high, the body cannot stablybe supported.

Then, in Documents 6 and 7, a kind of mesh structure is employed andhence this structure is easily deformed in the entirety. Thus, althougha high cushioning property is obtained, room for improvement in stablysupporting the body is concluded. On the other hand, the band plate ofDocument 5 does not excessively perform extensional deformation andhence excels in the stability of supporting the body. Nevertheless,since there is a limit in the elongation of each band plate, room forimprovement in the perspective of flexibility is concluded.

CITATION LIST Patent Literature

Patent Document 1: JP-A-2002-119366

Patent Document 2: JP-A-2004-129966

Patent Document 3: JP-A-2010-063831

Patent Document 4: U.S. Pat. No. 7,249,802

Patent Document 5: JP-A-2011-041615

Patent Document 6: Japanese Patent No. 4015673

Patent Document 7: U.S. Pat. No. 5,934,758

SUMMARY OF THE INVENTION Technical Problem

The invention of the present application has been devised in view ofsuch present situations and is intended to provide a chair in whichvalue in use has been enhanced and improvement has been achieved.Further, the present application includes a large number of improvedconfigurations and hence to provide these may be an object.

Further, the invention of the present application has been devised inview of such present situations. An object thereof is to provide a moreimproved backrest.

Solution to Problem

The present application is constructed from a group of inventions havinghierarchical and areal broadening. Then, typical modes thereof areidentified as a first to a fifteenth invention.

[First Invention]

Among these, the first invention constitutes a generic concept. Thebasic configuration thereof includes: a seat; a backrest; and a backframe having a rigid structure and arranged behind the backrest with aninterval in between. Then, the backrest is attached to the back frame bya first support device arranged at a height position close to an upperend of the backrest and by a second support device arranged at aposition lower than the first support device and higher than the seatsurface. Further, the first support device is attached to a part closeto a right-left middle part of the upper end part in the backrest.

Here, it is sufficient that the first support device is attached to theupper end of the backrest or a vicinity thereof. Thus, the backrest mayrun off over the first support device. That is, the attaching positionof the first support device has a vertical width. The second supportdevice is similar.

In the present invention, so to speak, the backrest is supported atthree positions consisting of the right-left middle part of the upperend part and of two right and left positions thereunder. Then, in a casethat the user sits down in a state of not leaning on the backrest inorder to perform desk work like PC operation, the lumbar and the likecan stably be supported by the portion supported at the two right andleft positions within the backrest. Thus, the state that the back isstraightened can appropriately be maintained and hence the user isallowed to take an appropriate working attitude.

On the other hand, the first support device is close to the right-leftmiddle part of the backrest and hence the upper end part (or the upperpart) of the backrest runs off to the outside in the right and leftdirections of the first support device so as to constitute free ends.That is, both right and left ends of the upper end part (the upper part)of the backrest serve as free ends not supported from the rear. Thus,when a configuration is employed that the upper part of the backrest canbe deformed by the body pressure, the backrest can be deformed such asto follow the twist of the body in a state of leaning on the backrest.This contributes to improvement in comfort in a leaning-on state.

[Second Invention]

The second invention is an example of expansion of the first invention.In this invention, the first support device has such an elastic strengththat, when the body pressure of a seat occupant acts on the backrest,permits warp deformation and thereby allows an upper part of thebackrest to move and deviate rearward, whereas the second support devicehas such a rigidity that, even when the body pressure of a seat occupantacts, bending deformation does not substantially occur or,alternatively, although elastic deformation is caused by the bodypressure of the seat occupant, the second support device has the elasticstrength with which a magnitude of the elastic deformation of the seconddevice is lower than that of the first support device.

In this second invention, the first support device has a springproperty. Thus, in a state that a person leans on the backrest, theupper part of the backrest is allowed to move such as to approach theback frame. That is, a reaction force of the first support device actson the upper part of the backrest from the rear and then this reactionforce provides a cushion effect and, hence, comfort to the user.Further, the deformation in the first support device permits twistdeformation in the backrest and hence also improves follow-updeformability in a case that the body is twisted in the right or leftdirection in a state that the person leans on the backrest.

Further, the second support device is hardly deformed by the bodypressure of a seat occupant or, alternatively, even in a case thatdeformation occurs, the magnitude thereof is smaller than that in thefirst support device. Thus, the function of supporting the body in aleaning-on state is appropriately achieved. Further, when the lower partof the backrest is excessively deformed in a leaning-on state such as arocking state, the stability of the body is degraded so that, in somecases, comfort is degraded on the contrary. However, in the secondinvention, even in a leaning-on state, the body is stably supported bythe lower part of the backrest and hence excessive movement of the bodyis prevented so that comfort can be improved.

[Third Invention]

The third invention is an example of expansion of the first invention orthe second invention. In this invention, the first support device is inan attitude elongated in up and down directions in side view, whereasthe second support device is separated into two right and left parts andthen the right and left second support devices are in such an inclinedattitude that an interval of the right and left second support devicesbecomes wider as going to a nearer side in plan view.

In the present invention, the first support device and the secondsupport device may employ various modes. However, when the thirdinvention is employed, in both of the first support device and thesecond support device, the portion extending between the back frame andthe backrest may be in a simple plate-shape configuration. This providesan advantage of simplified structure. Further, the first support device12 is elongated in the up and down directions and hence can easily bedeformed and bent rearward by the body pressure of a seat occupant.Thus, the follow-up property and the cushioning property against achange of the body can be improved.

[Fourth Invention]

The fourth invention is an example of expansion of the first inventionor the second invention. In this invention, the back frame includes apair of right and left vertically elongated members, these right andleft vertically elongated members being inclined such that an intervalbecomes narrow as going upward, and upper ends being connectedintegrally through a linkage part, and the first support device isattached to the linkage part of the back frame and the second supportdevice is attached to the right and left vertically elongated members.Here, the matter specific to the fourth invention may be applied also tothe third invention.

For example, the back frame may be constructed from one member locatedin the right-left middle part of the backrest or, alternatively, mayemploy a configuration of inverted U-shape having a right and a leftvertical part. However, when the configuration (the configuration ofinverted V-shape) of the fourth invention is employed, an advantage isobtained that a high strength can be ensured by employing a simpleconfiguration.

[Fifth Invention]

The fifth invention is an example of expansion of the first invention orthe second invention. In this invention, the backrest includes a mainmember fabricated from resin and attached to the back frame, the mainmember includes a framework having a loop shape and constituting anouter periphery and a body support part located in an inner sidethereof, and the body support part is provided with a large number ofslits or holes so as to have such a strength that deformation is easilycaused by the body pressure of a seat occupant. Here, the matterspecific to the fifth invention may be applied also to the thirdinvention or the fourth invention. The backrest may employ variousconfigurations. However, in the fifth invention, the main member iscomposed of an integrally molded article. Thus, in comparison with aconfiguration that the framework and the body support part areconstructed as separated members, the time and effort in manufacturingcan be saved and variation in the quality can also be prevented.

Here, in the fifth invention, the body support part is provided atconstant to the framework. However, as described above, a configurationmay also be employed that the body support part is constructed from aflexible raw material such as a mesh material and then the flexible rawmaterial is attached to the framework. In either case, it is preferablethat the framework performs warp deformation in accordance with the bodypressure of a seat occupant.

[Sixth Invention]

In the fifth invention, the backrest may be constructed from the mainmember alone and then the body pressure of the seat occupant may bereceived directly by the main member. In contrast, in the sixthinvention serving as an example of expansion of the fifth invention, acushion is arranged in the front face of the main member and then atleast the cushion is covered by a skin material. In this configurationof the fifth invention, softness to the body can be ensured by thecushion.

[Seventh Invention]

The seventh invention also is an example of expansion of the fifthinvention. In this invention, a lower end of the main member is locatedclose to the seat surface, a lumbar support member for supporting thelumbar of a seat occupant is arranged on the front face or the rear faceof the main member and, further, the main member is attached to thesecond support device at a position slightly higher than the lumbarsupport member. Here, the matter specific to the seventh invention maybe applied also to the first to the fourth invention or the sixthinvention.

When the lumbar support member is provided like in the seventhinvention, the lumbar of the seat occupant can appropriately besupported. Thus, this can contribute to maintaining of an appropriateattitude by the seat occupant. Then, since the first support device isattached to the main member on the lumbar support member, this can avoida situation that the width in the right and left directions of the mainmember becomes excessively large. Further, since the attaching part ofthe second support device and the attaching part of the lumbar supportmember are close to each other, the rigidity of the portion of theattaching part of the lumbar support member within the main member canalso be improved and hence this can contribute to the further stabilityof the body of the user.

[Eighth Invention]

The eighth invention is an example of expansion of the first inventionor the second invention. In this invention, when the body pressure of aseat occupant acts, the backrest is inclined rearward. The eighthinvention is applied to a rocking chair. However, obviously, the eighthinvention may be applied also to the third to the seventh invention. Inrocking chairs, a configuration is widely employed that the seat islinked to the backrest. Obviously, the present invention may be appliedalso to such a chair of synchronous type.

Warp deformation in the backrest appears remarkably in a rocking state.Thus, the effect of the present invention is utilized especially underthe eighth invention.

[Ninth Invention]

Among these, in a backrest of the ninth invention: a body support parton which a body pressure of a seat occupant acts is constructed from aplurality of areas divided into right and left with a certain amount ofinterval in between; each area is constructed from a large number ofstays horizontally elongated in the right and left directions; the staysin adjacent areas are arranged in a manner of being deviated in the upand down directions; adjacent stays in adjacent areas are linkedtogether by a linkage piece in an inclined attitude in front view; andthereby the inclined attitudes of linkage pieces adjacent in the up anddown directions are opposite to each other.

In the ninth invention, each stay is in an attitude horizontallyelongated in the right and left directions. Thus, basically, the bodysupport part deforms such as to extend in the right and left directionsalone. Thus, the configuration excels in the stability of supporting thebody. That is, the deformation in the body support part has directivityand hence a situation is avoided that the body support part excessivelyfollows the movement of the body so as to be deformed. Thus, theconfiguration excels in the stability of supporting the body.

Further, the linkage pieces are in an inclined attitude. Thus, when theattitudes of the linkage pieces vary so that the angle formed by linkagepieces adjacent in the up and down directions becomes small, theinterval of stays adjacent in the right and left directions becomeswide. This realizes substantially the same state as a situation that thebody support part has performed extensional deformation in the right andleft directions. By virtue of this, a high cushioning property can beensured. Further, each stay is deformed such as to be bent, twisted, orlike. Thus, the configuration excels also in the fit property to thebody.

[Tenth Invention]

In a backrest of the tenth invention, a group of stays are in alongitudinal orientation. That is, in the tenth invention: a bodysupport part on which the body pressure of a seat occupant acts isconstructed from a plurality of areas divided into up and down with acertain amount of interval in between; each area is constructed from alarge number of stays elongated vertically; the stays in adjacent areasare arranged in a manner of being deviated in the right and leftdirections; adjacent stays in adjacent areas are linked together by alinkage piece in an inclined attitude in front view; and thereby theinclined attitudes of linkage pieces adjacent in the right and leftdirections are opposite to each other.

In the eleventh invention, the body support part easily performsextensional deformation in the right and left directions. However,basically, the same effect as that of the ninth invention is obtained.

[Eleventh Invention]

The eleventh invention is a preferable example of expansion of the firstinvention or the second invention. In this invention, the width of thelinkage piece is smaller than the width of the stay in front view.According to this configuration, in a state that the supporting area forthe body is enlarged so that the stability of supporting the body isimproved, deformation in the linkage pieces is made easy so that thecushion can be improved.

[Twelfth Invention]

The twelfth invention is a detailed example of the ninth invention. Inthis invention, bases of linkage pieces adjacent in the up and down orthe right and left directions are close to each other so that thelinkage pieces adjacent in the up and down or the right and leftdirections are formed in a V-shape configuration.

The bases of linkage pieces adjacent in the up and down or the right andleft directions may be separate from each other. Nevertheless, in thiscase, the number of linkage pieces is reduced so that a possibilityarises that the strength is degraded. In contrast, in the configurationof the fourth invention, the linkage pieces are continuous to each otherwithout a gap in between. Thus, the number of linkage pieces can beincreased and hence the strength of the body support part also can beensured.

[Thirteenth Invention]

The thirteenth invention is detailed and preferable implementation ofthe ninth invention. In this invention, the configuration includes: acenter area located in a center in the right and left directions; andright and left side areas arranged on both right and left sides thereof,the center area being constructed from a group of center stays and theside area being constructed from side stays, wherein the group oflinkage pieces for connecting together the group of center stays and thegroup of side stays is formed in a zigzag configuration.

The number of areas constructing the body support part can arbitrarilybe set forth. Nevertheless, when an excessively large number of areas isemployed, the number of linkage pieces also increases and hence aconcern of excessively high flexibility is caused unless any means istaken. In contrast, like in the thirteenth invention, in a configurationconstructed from one center area and two side areas, the stability ofsupporting the body and the cushioning property can be harmonized witheach other in a satisfactory manner and hence this configuration ispreferable.

[Fourteenth Invention]

The fourteenth invention is detailed and preferable implementation ofthe ninth invention. In this invention, in the portion of the lumbarsupport part for supporting a vicinity of the lumbar of a seat occupant,the density of stays is high. In this invention, the lumbar of the seatoccupant is appropriately supported and hence this configuration isuseful in improvement of the stability of the body of the user. Here,also in the tenth invention, it is preferable to employ means forimproving the rigidity of the portion of the lumbar support part. Inboth the first invention and the second invention, as the means forimproves the rigidity of the lumbar support part, different means fromthe fourteenth invention may be employed like the plate thickness of thestay is increased.

[Fifteenth Invention]

The fifteenth invention also is detailed and preferable implementationof the ninth invention. In this invention, each stay has a plate-shapeconfiguration in which a plate thickness in the frontward and rearwarddirections is smaller than a vertical width, then a rib elongated in theright and left directions is formed in a rear face of each stay, andthen the rib also is connected integrally to the linkage piece.

In this fifteenth invention, in a state that each stay is made as thinas possible, necessary bending strength can be ensured. Thus, thisconfiguration is preferable for saving the material (the resin).Further, since the rib and the linkage piece are connected to eachother, smooth deformation can be realized with avoiding a situation thatbending is concentrated on the end part portion of the stay. Anotheradvantage is also obtained that stress concentration is prevented andhence durability is improved. Here, the configuration that a rib isprovided in the rear face of the stay may be applied also to the tenthinvention.

Effect of the Invention

By virtue of the present invention, comfort in a state of leaning on achair is improved. Further, the strength of the chair can be ensured,the time and effort in manufacturing can be saved, and variation in thequality can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams showing an overall external appearance of achair according to an embodiment. FIG. 1A is a perspective view takenfrom the front and FIG. 1B is a perspective view taken from the rear.

FIGS. 2A and 2B are diagrams showing an overall configuration of achair. FIG. 1A is a partly disassembled perspective view and FIG. 1B isa side view.

FIGS. 3A and 3B are disassembled views of a main part. FIG. 3A is adiagram in a state that a backrest is shifted in an ordinary attitude.FIG. 3B is a diagram in a state that the backrest is horizontallyrotated and disassembled.

FIGS. 4A to 4C are diagrams showing the relationship between a supportdevice and a back frame. FIG. 4A is a disassembled perspective view of afirst support device and a back frame, FIG. 4B is a disassembledperspective view of a first support device, a second support device, anda backrest, and FIG. 4C is a disassembled perspective view of a secondsupport device and a backrest.

FIGS. 5A and 5B are disassembled views showing the relationship betweena first support device and a backrest.

FIGS. 6A and 6B are disassembled views showing the relationship betweena second support device and a backrest.

FIGS. 7A to 7C are explanation diagrams of a lumbar support member.FIGS. 7A and 7B are disassembled perspective views and FIG. 7C is a planview of a backrest.

FIG. 8 is a front view of a backrest.

FIG. 9 is a perspective view of a backrest viewed from the front.

FIG. 10 is a perspective view of a backrest viewed from the rear.

FIG. 11 is a disassembled view used for describing the function.

DETAILED DESCRIPTION OF EMBODIMENTS

Next, an embodiment of the present invention is described below withreference to the drawings. The present embodiment is applied to a swivelchair widely used in offices or the like. Here, in the embodiment andthe claims given below, terms “frontward and rearward” and “right andleft” are used for identifying the directions. Then, these directionsare defined with reference to a person ordinarily sitting on the chair.

(1). Outlines of Chair

As shown in FIGS. 1A to 2B, a chair includes as main elements a legdevice 1, a seat 2, and a backrest 3. The backrest 3 is attached to aback frame 4 arranged behind it. The leg device 1 includes: a leg pillar5 in a vertical attitude; and a center tube 6 for supporting this. Fivebranched arms extend in radial directions from the center tube 6. Then,a caster is attached to the tip of each branched arm.

The leg pillar 5 is constructed from a gas cylinder of extendable typeprovided with an inner cylinder and an outer cylinder. As shown in FIG.2B, a base 7 is attach to the upper end of the leg pillar 5 and then theback frame 4 is linked through a joint member 8 to the base 7 in amanner permitting rearward inclination. Here, the back frame 4 and thejoint member 8 may be integrated together. The inner cylinder and theouter cylinder constituting the leg pillar 5 are freely rotatablerelatively. Thus, the base 7 (and the seat 2 and the backrest 3) isfreely rotatable horizontally.

Although illustration is omitted, a rocking spring for elasticallysupporting the rearward inclination of the back frame 4 is built in thebase 7. In the seat 2, an intermediate member (not shown) provided inthe base 7 is attached in a manner permitting rearward inclination andrearward movement about the front part serving as a center. Theintermediate member and the joint member 8 are linked together in amanner permitting relative movement by a shaft horizontally elongated inthe right and left directions. By virtue of this, the seat 2 performsrearward movement and rearward inclination in linkage with the rearwardinclination of the backrest 3.

The backrest 3 includes a main member fabricated from a raw material ofresin such as polypropylene by injection molding. In a case that thebackrest 3 includes a cushion and a skin material, the backrest 3 andthe main member need be distinguished from each other. However, in thepresent embodiment, the entirety of the backrest 3 is constructed fromthe main member and hence distinction of these does not provide asubstantial advantage. Thus, for simplicity of description, the term“main member” is not used and the term “backrest 3” is used.

The backrest 3 is constructed from a framework 9 constituting the outerperiphery and a body support part 10 located in the inside. As shown inFIG. 8, the framework 9 is formed in a shape substantially close to aquadrangle by: a pair of side members 9 a constituting both right andleft sides; an upper member 9 b horizontally elongated in the right andleft directions and constituting the upper end part; and a lower member9 c horizontally elongated in the right and left directions andconstituting the lower end.

The lower end of the backrest 3 is located close to the seat surface.Within the backrest 3, a lumbar support member 11 for supporting thelumbar of a seat occupant is arranged in the front face at a heightposition corresponding to the lumbar of the seat occupant. The bodyheight and the preference depend on the individual seat occupant. Thus,the lumbar support member 11 is in a height adjustable manner.

The backrest 3 of the present embodiment has such a constricted shapethat the attaching part of the lumbar support member 11 is thenarrowest. However, employable configurations need not be limited tothis. That is, as the configuration of the backrest 3, an arbitraryshape may be employed like: a configuration that the width in the rightand left directions is substantially fixed; the shape of an invertedtrapezium in which the upper end is wide and the lower end is narrow;and the shape of an inverted trapezium in which the upper end is narrowand the lower end is wide.

For example, as shown in FIGS. 3A and 3B, the back frame 4 includesright and left vertically elongated members 4 a inclined such that theinterval between these becomes close as going upward. In the right andleft vertically elongated members 4 a, the upper ends are connectedintegrally through a linkage part 4 b.

Thus, the right and left vertically elongated members 4 a constitute aconfiguration of inverted V-shape. The lower ends of the right and leftvertically elongated members 4 a are connected integrally through alower stay part 4 c. Further, a frontward arm part 4 d is providedintegrally at the lower end of the right and left vertically elongatedmembers 4 a. The frontward arm part 4 d and the lower stay part 4 c areconnected to the joint member 8 shown in FIG. 2A and 2B. For example, asclearly seen from FIG. 4B, the vertically elongated member 4 a of theback frame 4 is formed in an L-shaped cross section having a back faceplate and a side face plate. Thus, a light-weight structure is obtainedthat is strong in the frontward and rearward directions and the rightand left directions as well as against twist.

In the back frame 4 of the present invention, a resin molded article oran aluminum die-cast article is employed. Instead, fabrication may beperformed by employing a metal plate or a metallic pipe as the material.A composite article constructed from materials of different kinds may beemployed. Further, an integral construction is not unavoidable. That is,for example, the right and left vertically elongated members 4 a may beseparately fabricated and then linked together at the upper ends, thatis, may be constructed from a plurality of component parts. Ashell-structured article also may be employed as the back frame 4.

Then, for example, as shown in FIGS. 3A and 3B, within the backrest 3,the right-left middle part of the upper member 9 b is attached through afirst support device 12 to the linkage part 4 b of the upper end of theback frame 4. Then, in a part above the attaching part of the lumbarsupport member 11, the right and left side members 9 a are attachedthrough second support devices 13 to the vertically elongated member 4 aof the back frame 4. This point is described below in detail.

(2). Attaching Structure of Backrest

As shown in FIGS. 4A and 4B, the first support device 12 includes twospring parts 12 a arranged in a V-shape in front view. An upperattaching part 12 b horizontally elongated in the right and leftdirections is connected integrally to the upper ends of the spring parts12 a. Then, a lower attaching part 12 c protruding rearward is connectedintegrally to the lower ends of the right and left spring plate parts 12a. The first support device 12 is fabricated from a raw material ofresin such as polypropylene by injection molding. The spring plate parts12 a are in an attitude elongated in the up and down directions,however, has a plate shape which is wide in front view and narrow inside view. Thus, bending deformation can easily be caused by a forcefrom the front.

The lower attaching part 12 c is formed in the shape of a block (theshape of a boss) horizontally elongated in the right and leftdirections. A rear-side first recess 15 serving as a frontward apertureinto which the lower attaching part 12 c is fitted is formed in thelinkage part 4 b of the back frame 4. The lower attaching part 12 c isfixed with a first bolt 16 inserted into a rear-side first recess 15from below. As shown in FIG. 4A, in the attaching part 12 c of the firstsupport device 12, a nut insertion hole 17 into which a nut for thefirst bolt 16 is set is opened rearward.

As shown in FIGS. 5A and 5B, the upper member 9 b of the backrest 3 hasa triple structure in the inside and outside having an outer wall, aninner wall 18, and an intermediate wall 19. Thus, two elongated grooves20 opened rearward are formed. Then, the right-left middle part of theinner wall 19 is, for example, cut off so that a front-side first recess21 into which the upper attaching part 12 b of the first support device12 is fitted is formed. The upper attaching part 12 b of the firstsupport device 12 is fixed to the upper member 9 b with a second bolt 22inserted from below.

A nut holding part 23 opened rearward is formed in the upper member 9 bof the backrest 3. On the other hand, in the upper attaching part 12 bof the first support device 12, a stopper piece 24 for abutting againstthe nut holding part 23 of the upper member 9 b from the rear isprovided such as to protrude upward.

The second support device 13 is fabricated from a raw material of resinsuch as nylon resin having a high rigidity. Then, as shown in FIGS. 5Band 5C, the second support device 13 includes an arm part 13 a having aband plate shape gradually bent into a wave shape in plan view. At therear end of the arm part 13 a, a rear boss part 13 b is providedintegrally. Then, at the front end of the arm part 13 a, a front bosspart 13 c is provided integrally. The arm part 13 a has such a rigiditythat deformation is not easily caused by the body pressure of thesitting person (however, slight deformation may occur).

The rear boss part 13 b is fitted into the rear-side second recess 25provided in the vertically elongated member 4 a of the back frame 4. Athird bolt 26 is inserted into the rear-side second recess 25 frombelow. A nut (not shown) into which the third bolt 26 is inserted isincorporated in the rear boss part 13 b of the second support device 13.A flange 13 d overlapping with the opening edge of the rear-side secondrecess 25 is provided in the rear boss part 13 b.

As clearly shown in FIGS. 6A and 6B, a front-side second recess 27 intowhich a front boss 13 c of the second support device 13 is fitted isformed in the side member 9 a of the backrest 3. The front-side secondrecess 27 has a substantially box-shaped external appearance and then abolt hole 28 through which a bolt (not shown) is inserted is opened inthe inner wall 27 a. On the other hand, a nut attaching groove 29 isprovided in the front boss part 13 c of the second support device 13.Then, a bolt is inserted into the nut arranged in the nut attachinggroove 29.

In this case, a step part 30 for increasing the thickness of the portionof the bolt hole 28 so as to enhancing the strength is formed in aninner plate 25 a of the front-side second recess 27. On the other hand,a cut-off part 31 overlapping with the step part 30 of the front-sidesecond recess 27 is formed in the front boss part 13 c of the secondsupport device 13. Further, a flange 13 e overlapping with the openingedge of the front-side second recess 27 is provided in the front bosspart 13 c of the second support device 13.

(3). Lumbar Support Member

Next, the lumbar support member 11 is described below mainly withreference to FIGS. 7A to 7C. The lumbar support member 11 is composed ofa molded article fabricated from a raw material of resin and formed froma raw material such as polypropylene having certain elasticity. Then,the lumbar support member 11 has a shape horizontally elongated in theright and left directions and crossing the backrest 3. In plan view, thelumbar support member 11 is gradually curved concave frontward. Further,in vertical sectional side view, the lumbar support member 11 isslightly curved convex frontward.

Slide boss members 34 having a prism shape and protruding rearward areformed integrally at both right and left ends of the lumbar supportmember 11. The slide boss member 34 is fitted, in a freely slidablemanner, into a guide frame part 35 elongated in the up and downdirections provided in the side member 9 a of the backrest 3. As shownin FIGS. 6A and 6B, the inner periphery of the guide frame part 35 isconstructed from a plate part and then the front-side second recess 27described above is connected integrally to the upper end of the guideframe part 35.

As shown in FIGS. 7A to 7C, a frontward protruding part 36 a having ablock shape and provided in a knob 36 is fitted into the rear end of theslide boss member 34. The frontward protruding part 36 a of the knob 36is fixed to the slide boss member 34 with a bolt (not shown). A nutinsertion groove 37 is provided in the slide boss member 34. The lumbarsupport member 11 can be held in a manner that the height is adjustedstepwise. Then, as shown in FIG. 6A, as height adjusting means, a largenumber of stopper holes 38 are provided at a large number of verticalstages in the inner plate of the guide frame part 35.

Then, a configuration is widely employed that a lumbar support member isprovided in the backrest. However, in general, in many cases, the lumbarsupport member is arranged on the back side of a cushion or on the backside of a mesh material. Nevertheless, in a case that the cushion or themesh material intervenes between the lumbar support member and the body,in some cases, a person who desires a strong “feeling of abutting” feelsunsatisfaction. Further, in some cases like a case that the backrests isnot provided with a cushion or a mesh, a lumbar support member need bearranged on the near side of the back plate.

As an example of this, JP-A-2008-237333 discloses an approach that in aconfiguration that a backrest is constructed from a frame part and aback plate located in the inner side thereof and then a large number ofslits are provided in the back plate, a lumbar support member isarranged on the near side of the back plate. Further, this documentdiscloses a configuration that handles of clip type fitted onto a framepart from the outer side are provided integrally in both right and leftend parts of the lumbar support member and then the frame part iselastically held by the handles from below.

Nevertheless, in the configuration that the handles are fitted onto theframe part from outside like in the above-mentioned prior-art patentdocument, the handles run off to the right and left outer sides of theframe part and hence a trouble is expected that a person's clothes arecaught in the handle or, alternatively, an object abuts against thehandle so that the handle is damaged. Further, the handles maintain theheight merely by friction and hence a possibility arises that the lumbarsupport member is slid such as to be raised or lowered by the bodypressure of the seat occupant.

In contrast, in the present embodiment, the slide bosses 34 provided inboth right and left end parts of the lumbar support member 11 penetratethe guide frame parts 35 of the framework 9. Thus, the knobs 36 can bearranged such as not to run off the right and left outer sides of theframework 9. By virtue of this, a situation that the clothes are caughtin the knob 36 or, alternatively, an object abuts against it can beavoided or, alternatively, suppressed remarkably. Further, it is alsoeasy to provide height holding means constructed from the stopper holes38 for height adjustment of the guide frame part 35. Thus, the lumbarsupport member 11 can be held at a desired height in a manner notpermitting deviation movement.

Here, the height adjusting means may employ various configurations. In acase that the stopper holes 38 are provided in the guide frame part 35like in the embodiment, it is sufficient that an elastic member fittedinto and detached from the guide frame part 35 is provided in theblock-shaped frontward protruding part of the knob 36. The guide framepart 35 has a certain amount of frontward and rearward width and hencestrength degradation is not caused by the penetration of the slide bossmember 34. The knob 36 may be fabricated in a simple plate shape andthen may be screwed to the slide boss member 34.

(4). Structure of Backrest

Next, within the backrest 3, details of the structure of the bodysupport part 10 are described below mainly with reference to FIGS. 8 to10. As shown in FIG. 8, in the present embodiment, the body support part10 includes: groups of horizontally elongated side stays 40 connected tothe right and left side members 9 a; and a group of horizontallyelongated center stays 41 located between the groups of side stays 40.Both groups of stays 40 and 41 are arranged in a state of being deviatedup and down. The center area is constructed from the group of centerstays 41 and the side areas are constructed from the groups of sidestays 40.

Then, both right and left ends of the center stays 41 and the tips ofthe side stays 40 adjacent in the right and left directions areconnected integrally with linkage pieces (joint stays) 42. In this case,there are slight gaps in the right and left directions between the tipsof the side stays 40 and the ends of the center stays 41. Thus, thelinkage pieces (the joint stays) 42 are in an inclined attitude in frontview. Further, the center stays 41 and the side stays 40 are arranged ina manner of being deviated up and down and hence linkage pieces (jointstays) 42 adjacent in the up and down directions are in attitudes ofopposite orientation. Further, the bases of linkage pieces (the jointstays) 42 and stays 40 and 41 adjacent in the up and down directions areconnected integrally. Thus, the groups of linkage pieces (joint stays)42 have a zigzag shape in front view.

The backrest 3 is constricted such that the portion close to the lowerside becomes narrow in front view. Thus, together with the side members9 a of the backrest 3, a shape curved concave outward is formed.Further, the linkage pieces (the joint stays) 42 also are curved concaveoutward in front view such as to follow the shape of the side members 9a. Further, the side member 9 a and the center stay 41 havesubstantially the same length in the right and left directions.

The side stay 40 and the center stay 41 have a plate-shaped structurewhose front and rear faces are wide. However, as shown in FIG. 10, a rib43 is provided integrally in the rear faces of the side stay 40 and thecenter stay 41. Thus, the cross sections of the side stay 40 and thecenter stay 41 have a sideways T-shape. The rear face of the rib 43 isin plane with the rear face of the linkage piece (the joint stay) 42.The linkage piece (the joint stay) 42 has an external appearance of athin band plate and hence can easily be deformed such that the angle ofthe sideways V becomes wide or narrow. That is, in the lumbar supportmember 111, the density of stays 140 and 141 is high. By virtue of this,the lumbar support part has a higher rigidity than the other parts.

The groups of side stays 40 and center stays 41 are arranged at a largenumber of vertical stages. Thus, a space 44 horizontally elongated inthe right and left directions is opened individually between side stays40 and between center stays 41 adjacent in the up and down directions.Then, in the present embodiment, except for the lumbar support part, thevertical width dimension of the space 44 is twice or the like of thevertical width of the stay 40 or 41. In the lumbar support part, thevertical width dimension of the space 44 is set substantially at thesame level as the vertical width of the stay 40 or 41. Thus, the lumbarsupport part has a higher rigidity.

From the first, the vertical width and the pitch (the density) of theside stay 40 and the center stay 41 may be set up arbitrarily. Forexample, the vertical width dimension of the stay 40 or 41 and the space44 may be set substantially at the same level over the entirety in theup and down directions. Alternatively, the vertical width dimension ofthe stay 40 or 41 may be set smaller than the vertical width dimensionof the space 44 over the entirety.

Further, in the present embodiment, the body support part 10 has beenconstructed from two rows of the side stays 40 and one row of the centerstays 41. However, employable configurations need not be limited tothis. That is, the center stays 41 may be not provided and then the bodysupport part 10 may be constructed from right and left side stays 40 andfrom one linkage piece (one joint stay) 42 for connecting these.Alternatively, the body support part 10 may be constructed from two rowsof the side stays 40 and two rows of intermediate stays located betweenthem. In a case that two rows of the intermediate stays are provided,three linkage pieces (three joint stays) 42 are necessary. Further, thebody support part 10 may be constructed from five rows of stay groupsconsisting of two rows of the side stays 40, one row of the center stays41, and two rows of the intermediate stays. Further, the backrest 3 mayemploy other configurations.

(5). Summary

Next, the operation is described below with reference to FIG. 11. First,a rocking state is described below.

For example, the body pressure of a seat occupant in a rocking stateacts on the backrest 3 from the front as indicated by an arrow F. Then,the load acting on the backrest 3 is supported by the first supportdevice 12 and the second support device 13. Then, as indicated by anarrow Y, the first support device 12 can perform bending deformationsuch that the upper end is moved rearward by the load from the front inside view. On the other hand, as indicated by an arrow X, the secondsupport device 13 can perform bending deformation such that the tip ismoved rearward in plan view. However, since the second support device 13has a high rigidity, the back frame 4 of the backrest 3 is firmly heldby the second support device 13 and hence the lumbar of the seatoccupant is held with satisfactory stability.

On the other hand, the moment by rocking acts largely on the upper endpart in the backrest 3. However, the first support device 12 has a lowerrigidity than the second support device 13 and hence easily performswarp deformation in accordance with the body pressure. Thus, at the timeof rocking, the backrest 3 can perform warp deformation such that theupper end part thereof approaches the upper end part of the back frame4. This warp deformation of the backrest 3 can improve the cushioningproperty at the time of rocking.

Further, in a rocking state, when the person twists the upper half bodyin the right or left direction or, alternatively, shifts the shoulder inthe right or left direction, the two right and left spring parts 12 aconstituting the first support device 12 perform bending deformationunevenly so that the backrest 3 can be deformed and twisted such as tofollow the twist or the shift of the body. Thus, the backrest 3 canfollow the change of the attitude of the body. As a result, comfort canbe improved.

As clearly seen from FIG. 11, the backrest 3 is gradually curved concavefrontward in plan view. The degree of the curve is largest in thevicinity of the lumbar support member 11 and then the upper end part isin an almost flat state. Thus, in a state that the lumbar is held suchas not to be deviated right or left, the shoulder (or the portion closeto the shoulder) can easily be shifted right and left. Also from thispoint, high comfort can be obtained.

As shown in FIG. 2B, in a neutral state that the seat occupant does notlean on the backrest 3, the backrest 3 is slightly in a rearwardinclined attitude and the lumbar support member 11 is located on themost front side. Then, when the user performs desk work such as PCoperation, the user takes an attitude that the lumbar abuts against thelumbar support member 11 of the backrest 3. However, since the secondsupport device 13 has a high rigidity, the backrest 3 does not performwarp deformation in association with the body pressure of the seatoccupant in a neutral state and hence the lumbar of the person issupported by the backrest 3 with satisfactory stability. Thus, the upperhalf body of the user does not become unsteady and is held in apreferable attitude that the back is straightened. Thus, the presentconfiguration excels also in the attitude maintaining function in aneutral state (a non-rocking state).

Since the side stays 40 and the center stays 41 are deviated up and downand the linkage pieces (the joint stays) 42 are in a zigzagconfiguration, the backrest 3 of the present embodiment can perform warpdeformation such that the body support part 10 swells rearward inaccordance with the body pressure of the seat occupant. Thus, thepresent configuration excels in the fit property to the body of the userand excels also in the follow-up property for the movement of the body.

Further, when the linkage pieces (the joint stays) 42 adjacent in the upand down directions are deformed such that the mutual opening angle (theangle of V) becomes small, a tendency arises that the center stays 41are deviated rearward. As a result, the body support part 10 is deformedsuch as to swell rearward. This improves the cushioning and the fitproperty to the body of the user.

The present application is based on U.S. Provisional Application forPatent (61/831,763) filed on Jun. 6, 2013, the contents of which areincorporated herein by reference.

INDUSTRIAL APPLICABILITY

The present invention can provide a chair in which comfort in aleaning-on state is improved. Further, a chair can be provided in whichthe strength can be ensured, the time and effort in manufacturing can besaved, and variation in the quality can be prevented.

REFERENCE SIGN LIST

-   1 Leg device-   2 Seat-   3 Backrest-   4 Back frame-   5 Leg pillar-   6 Center tube-   7 Base-   8 Joint member-   9 Framework-   9 a Side member-   9 b Upper member-   9 c Lower member-   10 Body support part-   11 Lumbar support member-   12 First support device-   12 a Spring part-   12 b Upper attaching part-   12 c Lower attaching part-   13 Second support device-   13 a Arm part-   13 b Rear boss part-   13 c Front boss part-   13 e Flange-   15 Rear-side first recess-   16 First bolt-   18 Inner wall-   19 Intermediate wall-   22 Second bolt-   23 Nut holding part-   24 Stopper piece-   25 Rear-side second recess-   25 a Inner plate-   26 Third bolt-   27 Front-side second recess-   28 Bolt hole-   29 Nut attaching groove-   30 Step part-   31 Cut-off part-   34 Slide boss member-   35 Guide frame part-   36 Knob-   36 a Frontward protruding part-   37 Nut insertion groove-   38 Stopper hole-   40 Side stay-   41 Center stay-   42 Linkage piece-   43 Rib-   44 Space

1. A chair comprising: a seat; a backrest; and a back frame having arigid structure and arranged behind the backrest with an interval inbetween, wherein the backrest is attached to the back frame by a firstsupport device arranged at a height position close to an upper end ofthe backrest and by a second support device arranged at a position lowerthan the first support device and higher than a seat surface, the firstsupport device is attached to a part close to a right-left middle partof the upper end part in the backrest, and the second support device isattached to a left end part and a right end part of the backrest.
 2. Thechair according to claim 1, wherein the first support device has such anelastic strength that, when a body pressure of a seat occupant acts onthe backrest, permits warp deformation and thereby allows an upper partof the backrest to move and deviate rearward, whereas the second supportdevice has such a rigidity that, even when a body pressure of a seatoccupant acts, bending deformation does not substantially occur or,alternatively, although elastic deformation is caused by the bodypressure of the seat occupant, the second support device has the elasticstrength with which a magnitude of the elastic deformation of the secondsupport device is lower than that of the first support device.
 3. Thechair according to claim 1, wherein the first support device is in anattitude elongated in up and down directions in side view, whereas thesecond support device is separated into two right and left parts andthen the right and left second support devices are in such an inclinedattitude that an interval of the right and left second support devicesbecomes wider as going to a nearer side in plan view.
 4. The chairaccording to claim 1, wherein the back frame includes a pair of rightand left vertically elongated members, these right and left verticallyelongated members being inclined such that an interval becomes narrow asgoing upward, and upper ends being connected integrally through alinkage part, and the first support device is attached to the linkagepart of the back frame and the second support device is attached to theright and left vertically elongated members.
 5. The chair according toclaim 1, wherein the backrest includes a main member fabricated fromresin and attached to the back frame, the main member includes aframework having a loop shape and constituting an outer periphery and abody support part located in an inner side thereof, and the body supportpart is provided with a large number of slits or holes so as to havesuch a strength that deformation is easily caused by a body pressure ofa seat occupant.
 6. The chair according to claim 5, wherein a cushion isarranged in a front face of the main member and at least the cushion iscovered by a skin material.
 7. The chair according to claim 5, wherein alower end of the main member is located close to the seat surface, alumbar support member for supporting a lumbar portion of a seat occupantis arranged on the front face or the rear face of the main member and,further, the main member is attached to the second support device at aposition slightly higher than the lumbar support member.
 8. The chairaccording to claim 1, wherein when a body pressure of a seat occupantacts, the backrest is inclined rearward. 9-17. (canceled)